Typically, a flying shear, i.e. a severing device utilizing a shearing blade which travels with the workpiece, is used to sever sections from a continuously emitting workpiece. Shears of this type obtain the best results when used with relatively thin walled, small diameter workpieces and result in a rapid, clean-cut by the severing blade, leaving the workpiece end in a finished condition and eliminating the need for a recut operation. However, as the size and wall thickness of the workpiece increases, the stress developed during the cutting procedure also increases and becomes too great for a shear-type apparatus. Further, the increased stress results in a short blade life requiring costly tool replacement.
Alternate methods have been used to large diameter thick wall pipe, including saws, electrical arc or gas cutting. Again, these devices must travel with the workpiece during the cutting operation. The slow cutting speeds of these devices combined with the high rate of speed at which the pipe emanates from the mill, results in a long distance of travel to perform the cutting operation and a corresponding increase in mill space. Further, the minimum length of a section of pipe that may be severed is also increased, resulting in the need for a recut operation to obtain shorter lengths. Further, these devices are high maintenance devices which require constant maintenance; i.e., the replacement of saw blades, electrodes or gas.
It is known in the art to sever a metal workpiece into parts by contacting the workpiece with electrical contacts and supply high frequency electrical current through the contacts to heat the workpiece thereby reducing the tensile strength of the workpiece in the heated area. The workpiece may then be pulled apart in the heated area. See, for example, U.S. Pat. No. 4,916,278. However, there is a need for an apparatus to effectively sever a moving workpiece by heating the material to a temperature at which the tensile strength is substantially reduced and using a mechanical force to pull the workpiece apart.
Accordingly, it is an object of applicant's invention to provide a bladeless, quick and efficient severing means which travels with the workpiece during the severing operation, to sever large diameter, thick wall pipe without requiring a long carriage to support the severing means. Further, it is also an object of applicant's invention to eliminate any recut operation for reducing the pipe sections to shorter lengths.
Additionally, it is an object of the present invention to provide an apparatus for effectively heating the workpiece to reduce the tensile strength of the workpiece and a mechanical force to pull the workpiece apart in the heated area.